Apple's rejection of the Google Voice iPhone application and the removal of 3rd party clients proved to be the last straw, and now the Federal Communications Commission is involved. The FCC has begun an investigation into the matter. "The Federal Communications Commission has a mission to foster a competitive wireless marketplace, protect and empower consumers, and promote innovation and investment," FCC Chairman Julius Genachowski said, "Recent news reports raise questions about practices in the mobile marketplace."

The Google Voice applications were all pulled from the App Store earlier this week, with Apple citing its usual bogus reason that it duplicated functionality. While Apple remains mute on the issue, the legions of iPhone users were quick to point the finger at AT&T, but they later denied any involvement, claiming they have no power over the App Store.

The FCC isn't buying all this, and has started an investigation into the matter. They sent a letter to each of the three companies involved (Apple, AT&T, and Google) in which they ask for various clarifications. The companies must answer the various questions before August 21.

From Apple, the FCC would like to know why the Google Voice applications were removed, why Google's own client was rejected from the App Store, and whether or not any other related applications were removed. In addition, the FCC would like contact information for the involved developers. They're also interested in any differences between Google Voice and other VoIP applications that did get approved for the App Store.

They also want to know if Apple did this in consultation with AT&T, or whether they acted alone. On a more general note, they also want to know if AT&T has any influence in the App Store approval process, whether in general or for specific applications.

But this isn't all. The FCC is also interested in the App Store beyond just the Google Voice issue. The FCC wants to know the criteria for App Store rejection, the details of the submission process, the amount of rejected applications, a list of those applications, and so on.

From Google, the FCC wants a description of the rejected official client, and what reasoning Apple gave to Google for the rejection (if any). They're also interested in any other possible Google applications that did make their way into the App Store. Android also comes into play, as the FCC wants to know the details about Adroid's approval process.

When it comes to AT&T, there's a lot of overlap with the letter to Apple, but there are also additional questions about any possible agreements between AT&T and Apple regarding the use of the 3G network. The FCC is also interested in any contractual limitations on network usage in customer contracts. Another important item is whether or not Google Voice is allowed on other handsets on AT&T's network.

It's funny how Google's very own Eric Schmidt more or less predicted this mess back in 2007 when he wrote to the FCC, asking them to implement open standards that would give users the freedom to use whatever application on whatever device on whatever network.